80 BUTTER-MAKING. 
upon the judgment of the receiver, and in a great measure 
upon the local conditions. Some of the creameries have no 
facilities for handling different grades of milk, and some sell 
butter on a market where no sharp distinction is made between 
good and poor butter. Others have, through experience, sat- 
isfied themselves that under American creamery conditions 
it does not pay to make too many grades, nor does it pay to 
grade too closely. Two, or at the most three, grades of but- 
ter can at times be manufactured in one creamery profitably. 
It is advisable to reject sour and abnormal milk. If accepted, 
it should not be mixed with the remainder of the milk, as it 
might contaminate all of it; or, the sour milk might cause 
coagulation, and thereby clog up the separators. If a can of 
milk is sour, but otherwise clean, it is not necessarily unfit 
for the production of first-class butter. If retained until after 
the sweet milk has been skimmed, it may be run through 
the separator successfully. 
2. The Use of Acid Tests—Some creameries, especially 
the larger central cream plants, are now grading the milk or 
cream according to the amount of acid it contains. For instance, 
cream or milk containing .2% acid or less is classed as first 
grade; that containing from .2 to .4% as second grade, and 
the cream containing more than 4% acid as third grade. 
Mann’s and Farrington’s acid tests can both be used, but a 
more rapid and convenient way is to use a solution prepared 
from Farrington’s tablets. The solution is prepared by taking 
one tablet for each ounce of warm water and allowing the 
tablets to dissolve. When one part of this alkaline solution 
and one part of milk are put together in a cup and mixed 
and the solution still retains a pink color, it shows that there 
is less than .1% acid in the sample tested. If two parts of 
alkali and one part of milk are mixed and the mixture remains 
pink, then there is less than .2% of acid. If the mixture turns 
colorless, it shows there is more than .2% acid in the sample. 
If three measures of alkali to one measure of milk are taken, 
and the mixture remains pink, that indicates that there is 
